Originally Posted by Captain Nemo

Alien, filing "married filing separately" will not help you if you and your wife are in approximately the same income level. If you look at the rate structure, they effectively took the various tiered income levels and cut them in half for the Married Filing Separately table.

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Just a rough approximation, as I didn't factor in itemized/standard deduction and personal exemptions. Also, married filing separately is used, for example, when one spouse has income greatly in excess of the other